A package that overrides `length()` cannot be rendered

Run the reproducer with pkgdown::build_site, then trace the failure from pkgdown:::build_site_local through build_reference, render_page, and data_navbar. Compare the package's exported length() in R/length.R with the reference input man/length.Rd; done means the function reference renders without calling the package's length().

Real-world usage: https://github.com/cynkra/dd . I really wonder what's happening under the hood.

pkg <- file.path(tempdir(), "pkglength")
dir.create(file.path(pkg, "R"), recursive = TRUE, showWarnings = FALSE)

writeLines(c(
  "Package: pkglength",
  "Title: Minimal Package That Exports length()",
  "Version: 0.0.1",
  "Authors@R: person('A', 'B', email = 'a@b.com', role = c('aut', 'cre'))",
  "Description: Reproduces a pkgdown build failure.",
  "License: MIT + file LICENSE",
  "Encoding: UTF-8"
), file.path(pkg, "DESCRIPTION"))

writeLines(c("YEAR: 2026", "COPYRIGHT HOLDER: A B"), file.path(pkg, "LICENSE"))
writeLines("export(length)", file.path(pkg, "NAMESPACE"))
writeLines(c(
  "#' A length() stub",
  "#' @param x Ignored.",
  "#' @return Never returns.",
  "#' @name length",
  "#' @export",
  "length <- function(x) stop('pkglength::length() is not meant to be called')"
), file.path(pkg, "R", "length.R"))

# a man page so as_pkgdown() has a topic to parse
dir.create(file.path(pkg, "man"))
writeLines(c(
  "\\name{length}", "\\alias{length}", "\\title{A length() stub}",
  "\\usage{length(x)}", "\\arguments{\\item{x}{Ignored.}}",
  "\\description{A length() stub.}"
), file.path(pkg, "man", "length.Rd"))

lib <- file.path(tempdir(), "lib")
dir.create(lib, showWarnings = FALSE)
install.packages(pkg, repos = NULL, type = "source", lib = lib)

withr::with_libpaths(lib, action = "prefix", {
  # Real-world entry point (this is what users hit):
  pkgdown::build_site(pkg, new_process = FALSE, install = FALSE)
})
#> ── Initialising site ───────────────────────────────────────────────────────────
#> Copying <pkgdown>/BS3/assets/bootstrap-toc.css to bootstrap-toc.css
#> Copying <pkgdown>/BS3/assets/bootstrap-toc.js to bootstrap-toc.js
#> Copying <pkgdown>/BS3/assets/docsearch.css to docsearch.css
#> Copying <pkgdown>/BS3/assets/docsearch.js to docsearch.js
#> Copying <pkgdown>/BS3/assets/link.svg to link.svg
#> Copying <pkgdown>/BS3/assets/pkgdown.css to pkgdown.css
#> Copying <pkgdown>/BS3/assets/pkgdown.js to pkgdown.js
#> ── Building pkgdown site for package pkglength ─────────────────────────────────
#> 
#> Reading from:
#> /var/folders/dj/yhk9rkx97wn_ykqtnmk18xvc0000gn/T/RtmpIh9aw1/pkglength
#> Writing to:
#> /var/folders/dj/yhk9rkx97wn_ykqtnmk18xvc0000gn/T/RtmpIh9aw1/pkglength/docs
#> ── Sitrep ──────────────────────────────────────────────────────────────────────
#> 
#> ✖ Bootstrap 3 is deprecated; please switch to Bootstrap 5.
#> ℹ Learn more at
#>   <https://www.tidyverse.org/blog/2021/12/pkgdown-2-0-0/#bootstrap-5>.
#> ✖ URLs not ok.
#>   No '_pkgdown.yml' found.
#>   See details in `vignette(pkgdown::metadata)`.
#> ✔ Favicons ok.
#> ✔ Open graph metadata ok.
#> ✔ Articles metadata ok.
#> ✔ Reference metadata ok.
#> ── Initialising site ───────────────────────────────────────────────────────────
#> 
#> ── Building home ───────────────────────────────────────────────────────────────
#> 
#> Writing `authors.html`
#> Writing `LICENSE-text.html`
#> Reading 'DESCRIPTION'
#> Writing `index.html`
#> Writing `404.html`
#> ── Building function reference ─────────────────────────────────────────────────
#> 
#> Writing `reference/index.html`
#> 
#> Attaching package: 'pkglength'
#> 
#> 
#> The following object is masked from 'package:base':
#> 
#>     length
#> 
#> 
#> Reading man/length.Rd
#> Error in `length()`:
#> ! pkglength::length() is not meant to be called

rlang::last_trace()
#> <error/rlang_error>
#> Error in `length()`:
#> ! pkglength::length() is not meant to be called
#> ---
#> Backtrace:
#>      ▆
#>   1. ├─withr::with_libpaths(...)
#>   2. │ └─base::force(code)
#>   3. ├─pkgdown::build_site(pkg, new_process = FALSE, install = FALSE)
#>   4. │ └─pkgdown:::build_site_local(...)
#>   5. │   └─pkgdown::build_reference(...)
#>   6. │     ├─pkgdown:::unwrap_purrr_error(...)
#>   7. │     │ └─base::withCallingHandlers(...)
#>   8. │     └─purrr::map(...)
#>   9. │       └─purrr:::map_("list", .x, .f, ..., .progress = .progress)
#>  10. │         ├─purrr:::with_indexed_errors(...)
#>  11. │         │ └─base::withCallingHandlers(...)
#>  12. │         ├─purrr:::call_with_cleanup(...)
#>  13. │         └─pkgdown (local) .f(.x[[i]], ...)
#>  14. │           └─pkgdown::render_page(...)
#>  15. │             └─pkgdown:::render_page_html(pkg, name = name, data = data, depth = depth)
#>  16. │               ├─pkgdown:::modify_list(data_template(pkg, depth = depth), data)
#>  17. │               └─pkgdown::data_template(pkg, depth = depth)
#>  18. │                 └─pkgdown:::data_navbar(pkg, depth = depth)
#>  19. │                   └─pkgdown:::navbar_links(pkg, depth = depth, call = call)
#>  20. │                     └─pkgdown:::navbar_link_components(pkg, call = call)
#>  21. │                       ├─base::intersect(...)
#>  22. │                       └─pkgdown:::config_pluck_character(...)
#>  23. │                         └─pkgdown:::config_pluck(pkg, path, default)
#>  24. │                           └─purrr::pluck(pkg$meta, !!!where, .default = default)
#>  25. │                             └─purrr:::pluck_raw(.x, list2(...), .default = .default)
#>  26. ├─pkglength::length(`<prnt_yml>`)
#>  27. │ └─base::stop("pkglength::length() is not meant to be called") at pkglength/R/length.R:6:11
#>  28. ├─base::.handleSimpleError(...)
#>  29. │ └─purrr (local) h(simpleError(msg, call))
#>  30. │   └─cli::cli_abort(...)
#>  31. │     └─rlang::abort(...)
#>  32. │       └─rlang:::signal_abort(cnd, .file)
#>  33. │         └─base::signalCondition(cnd)
#>  34. └─pkgdown (local) `<fn>`(`<prrr_rr_>`)
#>  35.   └─rlang::cnd_signal(err$parent)
#>  36.     └─rlang:::signal_abort(cnd)

^{Created on 2026-07-24 with reprex v2.1.1}